1) Field of the Invention
The present invention relates to a technology for correcting a shift, in a recording position on a recording medium, arising due to a shift in a center of rotation of the recording medium.
2) Description of the Related Art
A servo signal is used to position a magnetic head on a recording medium in a magnetic disk apparatus. Over the years, the number of tracks on the recording media have increased in response to a need for improving the recording density. Consequently, the time to write the servo signal on the track (hereinafter, “write time of the servo signal”) has increased and has led to a decline in the productivity of the magnetic disks.
One approach to write the servo signal is to incorporate the recording medium in the magnetic disk apparatus, and write the servo signal on the recording medium with the head. However, in this case, since writing of the servo signal is performed by each magnetic disk apparatus separately, the structure of the magnetic disk apparatus becomes complicated and the cost also increases.
Japanese Patent Laid-Open Publication No. H4-251440 (see page 2) discloses a technology to write the servo signal, by means of, for example, magnetic transcription. The writing of the servo signal is performed collectively. Precisely, a master disk on which the servo signal is recorded is attached to other disks, and a magnetic field is applied to the disks. As a result, the servo signal is batch-transcribed to the other disks.
Sometimes the center of rotation of the recording medium shifts from the true center of rotation when the recording medium is incorporated in the magnetic disk apparatus. When there is a shift in the center of rotation, the recording medium rotates with respect to the head at a speed that is different from the desired speed. As a result, the head is positioned on the recording medium at a position that is different from the desired position (hereinafter, “shift in the data writing position”). The shift in the center of rotation of the recording medium may be caused of an external impact.
One approach to take into account the shift in the data writing position due to the shift in the center of rotation is to increase a space between sectors on the recording medium.